/* ---------------------------------------------------------------------- * Copyright (C) 2010 ARM Limited. All rights reserved. * * $Date: 15. July 2011 * $Revision: V1.0.10 * * Project: CMSIS DSP Library * Title: arm_shift_q31.c * * Description: Shifts the elements of a Q31 vector by a specified number of bits. * * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 * * Version 1.0.10 2011/7/15 * Big Endian support added and Merged M0 and M3/M4 Source code. * * Version 1.0.3 2010/11/29 * Re-organized the CMSIS folders and updated documentation. * * Version 1.0.2 2010/11/11 * Documentation updated. * * Version 1.0.1 2010/10/05 * Production release and review comments incorporated. * * Version 1.0.0 2010/09/20 * Production release and review comments incorporated. * * Version 0.0.7 2010/06/10 * Misra-C changes done * -------------------------------------------------------------------- */ #include "arm_math.h" /** * @ingroup groupMath */ /** * @defgroup shift Vector Shift * * Shifts the elements of a fixed-point vector by a specified number of bits. * There are separate functions for Q7, Q15, and Q31 data types. * The underlying algorithm used is: * *
* pDst[n] = pSrc[n] << shift, 0 <= n < blockSize. ** * If
shift
is positive then the elements of the vector are shifted to the left.
* If shift
is negative then the elements of the vector are shifted to the right.
*/
/**
* @addtogroup shift
* @{
*/
/**
* @brief Shifts the elements of a Q31 vector a specified number of bits.
* @param[in] *pSrc points to the input vector
* @param[in] shiftBits number of bits to shift. A positive value shifts left; a negative value shifts right.
* @param[out] *pDst points to the output vector
* @param[in] blockSize number of samples in the vector
* @return none.
*
*
* Scaling and Overflow Behavior:
* \par
* The function uses saturating arithmetic.
* Results outside of the allowable Q31 range [0x80000000 0x7FFFFFFF] will be saturated.
*/
void arm_shift_q31(
q31_t * pSrc,
int8_t shiftBits,
q31_t * pDst,
uint32_t blockSize)
{
uint32_t blkCnt; /* loop counter */
uint8_t sign; /* Sign of shiftBits */
/* Getting the sign of shiftBits */
sign = (shiftBits & 0x80);
#ifndef ARM_MATH_CM0
/* Run the below code for Cortex-M4 and Cortex-M3 */
/*loop Unrolling */
blkCnt = blockSize >> 2u;
/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
** a second loop below computes the remaining 1 to 3 samples. */
while(blkCnt > 0u)
{
/* C = A (>> or <<) shiftBits */
/* Shift the input and then store the results in the destination buffer. */
*pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
(*pSrc++ >> -shiftBits);
*pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
(*pSrc++ >> -shiftBits);
*pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
(*pSrc++ >> -shiftBits);
*pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
(*pSrc++ >> -shiftBits);
/* Decrement the loop counter */
blkCnt--;
}
/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
** No loop unrolling is used. */
blkCnt = blockSize % 0x4u;
#else
/* Run the below code for Cortex-M0 */
/* Initialize blkCnt with number of samples */
blkCnt = blockSize;
#endif /* #ifndef ARM_MATH_CM0 */
while(blkCnt > 0u)
{
/* C = A (>> or <<) shiftBits */
/* Shift the input and then store the result in the destination buffer. */
*pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
(*pSrc++ >> -shiftBits);
/* Decrement the loop counter */
blkCnt--;
}
}
/**
* @} end of shift group
*/